Spriteling
The Spritelings are forest sprites who assist Wario in Wario World. They come in five colors and will give him hints and tips to defeat The Black Jewel if he rescues them from their cage prisons. Despite their friendly demeanor, they are for some reason listed in the enemies section of the Wario World instruction manual; however, Wario claims that this is because they are his "enemies' enemies".
Each of the eight levels in Wario World contains five Spritelings to rescue, for a total of forty in the game.
Wario seems to show dislike for the sprites, preoccupying himself with things of greater importance (i.e. regaining his treasure). However, it is the Spritelings that rebuild Wario's ruined castle at the end of the game, and the more Spritelings Wario rescued throughout the course of the game, the better his new castle will be.